Question: Tiffany is 3 times as old as Daniel and is also 18 years older than Daniel. How old is Tiffany?
Explanation: We can use the given information to write down two equations that describe the ages of Tiffany and Daniel. Let Tiffany's current age be $t$ and Daniel's current age be $d$ $t = 3d$ $t = d + 18$ Now we have two independent equations, and we can solve for our two unknowns. One way to solve for $t$ is to solve the second equation for $d$ and substitute that value into the first equation. Solving our second equation for $d$ , we get: $d = t - 18$ . Substituting this into our first equation, we get the equation: $t = 3$ $(t - 18)$ which combines the information about $t$ from both of our original equations. Simplifying the right side of this equation, we get: $t = 3t - 54$ Solving for $t$ , we get: $2 t = 54$ $t = 27$.